InfiniteIntravascular Ultrasound(IVUS) vs Angiography Guided Percutaneous Coronary Intervention(PCI) for Patients With Left Main Bifurcation Lesion

616 patients with primary left main coronary artery bifurcation lesions will be recruited in this study. The target lesions of patients need to be true coronary artery bifurcation lesions (Medina 1,1,1 or 0,1,1). After angiography, patients will be randomly assigned to intravascular ultrasound(IVUS) - guided and coronary angiography (CAG)- guided groups. The random number of patients will be generated by the central computer random system, and the random will be stratified according to the study sites. In coronary angiography(CAG)-guided group, two-stent technique will be used(the exact two-stent technique used was left to the operator's discretion). In intravascular ultrasound(IVUS)-guided group, minimal lumen area(MLA) in ostium of side branch will be measured by intravascular ultrasound(IVUS). If minimal lumen area(MLA)<4mm2, two-stent technique will be used(the exact two-stent technique used was left to the operator's discretion) and intravascular ultrasound(IVUS) will be repeated at the end of the procedure. If minimal lumen area(MLA) >=4mm2, one-stent technique will be used and intravascular ultrasound(IVUS) will be repeated. If minimal lumen area(MLA) in ostium of side branch is still >=4mm2, the procedure will be ended. If minimal lumen area(MLA) in ostium of side branch become <4mm2, the following interventional strategy will be left to the operator's discretion( balloon inflation, drug-eluting balloon, or switch to two-stent technique). Again, intravascular ultrasound(IVUS) will be repeated at the end of the procedure.